Next Issue

E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Table of Contents

Int. J. Mol. Sci., Volume 6, Issue 1 (January-February 2005), Pages 1-176

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-15
Export citation of selected articles as:

Editorial

Jump to: Research

Open AccessEditorial Special Issue Dedicated to Professor Marvin Charton – Correlation Analyst Par Excellence
Int. J. Mol. Sci. 2005, 6(1), 1-2; doi:10.3390/i6010001
Received: 18 January 2005 / Published: 31 January 2005
PDF Full-text (121 KB) | HTML Full-text | XML Full-text

Research

Jump to: Editorial

Open AccessArticle Marvin Charton - Correlation Analyst Par Excellence
Int. J. Mol. Sci. 2005, 6(1), 3-10; doi:10.3390/i6010003
Received: 10 September 2004 / Accepted: 19 October 2004 / Published: 31 January 2005
PDF Full-text (187 KB) | HTML Full-text | XML Full-text
Abstract Since the late 1950s Marvin Charton, physical organic chemist, of Pratt Institute, Brooklyn, New York has studied structure-property relationships through correlation analysis, and has become one of the leading authorities in this field. Full article
Open AccessArticle Substituent Effects in the 13C-NMR Spectra of Six-Membered Nitrogen Heteroaromatic Compounds
Int. J. Mol. Sci. 2005, 6(1), 11-17; doi:10.3390/i6010011
Received: 15 June 2004 / Revised: 25 January 2005 / Accepted: 26 January 2005 / Published: 31 January 2005
Cited by 2 | PDF Full-text (169 KB) | HTML Full-text | XML Full-text
Abstract
It is shown that the 13C-NMR chemical shifts of carbon atoms in substituted sixmembered heteroaromatic compounds correlate with the correponding "additivity parameters" for substituted benzene derivatives. Thus, for precalculation of chemical shifts in such compounds, just one set of parameters can [...] Read more.
It is shown that the 13C-NMR chemical shifts of carbon atoms in substituted sixmembered heteroaromatic compounds correlate with the correponding "additivity parameters" for substituted benzene derivatives. Thus, for precalculation of chemical shifts in such compounds, just one set of parameters can be used. The differences between experimental chemical shifts and those calculated from correlation with the common set may provide insights into intramolecular interactions not reported in the literature. Full article
Open AccessArticle Re-examination of Steric Substituent Constants by Molecular Mechanics
Int. J. Mol. Sci. 2005, 6(1), 18-29; doi:10.3390/i6010018
Received: 1 July 2004 / Revised: 10 September 2004 / Accepted: 12 October 2004 / Published: 31 January 2005
Cited by 2 | PDF Full-text (273 KB) | HTML Full-text | XML Full-text
Abstract
Statistical analysis employing the set of the steric constants Ωj,k(Rc) is shown to be very effective in characterizing the substituent steric effect on organic reactions. Ωj,k(Rc) contains several variable parameters which are useful for [...] Read more.
Statistical analysis employing the set of the steric constants Ωj,k(Rc) is shown to be very effective in characterizing the substituent steric effect on organic reactions. Ωj,k(Rc) contains several variable parameters which are useful for the diagnosis of the character of steric effect. The parameters controlling the angular, or directional, weight (j,k) and the size of reaction center atom X(Rc) are varied in order to elucidate the characteristics of several steric substituent constants. Full article
Open AccessArticle Kinetics and Mechanism of Acetoxymercuration and Acid-Catalysed Hydration of α-Alkylstyrenes
Int. J. Mol. Sci. 2005, 6(1), 30-44; doi:10.3390/i6010030
Received: 15 April 2004 / Revised: 10 January 2005 / Accepted: 10 January 2005 / Published: 31 January 2005
Cited by 1 | PDF Full-text (273 KB) | HTML Full-text | XML Full-text
Abstract
Nine α-alkylstyrenes carrying the following substituents have been synthesised: methyl, ethyl, propyl, butyl, pentyl, isobutyl, isopropyl, sec-butyl and tert-butyl. Kinetics has been measured for the reaction of these compounds with mercuric acetate in anhydrous acetic acid at 25 °C. The rate constants [...] Read more.
Nine α-alkylstyrenes carrying the following substituents have been synthesised: methyl, ethyl, propyl, butyl, pentyl, isobutyl, isopropyl, sec-butyl and tert-butyl. Kinetics has been measured for the reaction of these compounds with mercuric acetate in anhydrous acetic acid at 25 °C. The rate constants are very sensitive to inductive effects (ρI = –49.5 in AISE theory) and steric effects (ψ = –1.59 according to Charton). These results support the presumed existence of an intermediate with an asymmetrically bound acetylmercuric cation to carbon atoms of the vinyl group of styrene. The kinetics of an acid-catalysed hydration of the above-mentioned α-alkylstyrenes were also measured in aqueous sulphuric acid at 25 °C. The derivatives exhibited kinetically a consecutive isomerisation reaction giving the more stable substituted styrenes. The values of the slope mm* of the dependence upon the excess acidity function (X) were evaluated, and exceptionally low values were found for the butyl and pentyl substituents (1.02 and 0.73, respectively), while on the other hand tert-butyl showed an exceptionally high value (3.28). On the basis of the facts, a mechanism has been suggested for the acid-catalysed hydration, involving the reaction of a relatively stable and sterically hindered carbocation with water as the rate-limiting step of the reaction. Full article
Open AccessArticle How the Substituent Effect Influences π-Electron Delocalisation in the Ring of Reactants in the Reaction Defining the Hammett Substituent Constants σm and σp
Int. J. Mol. Sci. 2005, 6(1), 45-51; doi:10.3390/i6010045
Received: 29 April 2004 / Accepted: 9 October 2004 / Published: 31 January 2005
Cited by 18 | PDF Full-text (195 KB) | HTML Full-text | XML Full-text
Abstract
Application of the geometry (HOMA, EN, GEO) and magnetism based (NICS, NICS(1)) indices of aromaticity to optimised geometry of the ring in 12 meta – and 12 para – substituted benzoic acids and their anions by use of DFT computations at B3LYP/6-311+G(d,p) [...] Read more.
Application of the geometry (HOMA, EN, GEO) and magnetism based (NICS, NICS(1)) indices of aromaticity to optimised geometry of the ring in 12 meta – and 12 para – substituted benzoic acids and their anions by use of DFT computations at B3LYP/6-311+G(d,p) level has shown a very low substituent effect on the π-electron delocalisation. This resembles (qualitatively) the resistance of benzene (and typical aromatic systems) against reactions leading to the change of π-electron delocalisation. Full article
Open AccessArticle 13C-NMR Based Evaluation of the Electronic and Steric Interactions in Aromatic Amines
Int. J. Mol. Sci. 2005, 6(1), 52-62; doi:10.3390/i6010052
Received: 16 April 2004 / Revised: 24 January 2005 / Accepted: 25 January 2005 / Published: 31 January 2005
Cited by 10 | PDF Full-text (211 KB) | HTML Full-text | XML Full-text
Abstract
Chemical shifts of the para carbon atoms, δ(13C-4), in a series of aromatic amines were used to calculate the σp, σR and σOR substituent constants for different amino groups. 1-Pyrrolidino, N,N-di-n-butylamino and N,N-diethylamino groups were [...] Read more.
Chemical shifts of the para carbon atoms, δ(13C-4), in a series of aromatic amines were used to calculate the σp, σR and σOR substituent constants for different amino groups. 1-Pyrrolidino, N,N-di-n-butylamino and N,N-diethylamino groups were found to be the most strong electron-donors. ortho-Substitution decreases the donor properties of the amino group. The amino groups in 2,6-di-i-propylaniline and N,N-2,6-tetramethylaniline have very weak electron-donor properties. The nitrogen atom in benzoquinuclidine and N,N-dimethyl-2,6-di-i-propylaniline have an electron-acceptor character. The calculated substituent constants of the amino groups studied are consistent with the spectral and reactivity data available in literature. Values of δ(15N) cannot be used as a direct measure of electronic effects of the N atom in anilines. Full article
Open AccessArticle Inductive QSAR Descriptors. Distinguishing Compounds with Antibacterial Activity by Artificial Neural Networks
Int. J. Mol. Sci. 2005, 6(1), 63-86; doi:10.3390/i6010063
Received: 20 September 2004 / Revised: 14 January 2005 / Accepted: 15 January 2005 / Published: 31 January 2005
Cited by 20 | PDF Full-text (307 KB) | HTML Full-text | XML Full-text
Abstract
On the basis of the previous models of inductive and steric effects, ‘inductive’ electronegativity and molecular capacitance, a range of new ‘inductive’ QSAR descriptors has been derived. These molecular parameters are easily accessible from electronegativities and covalent radii of the constituent atoms [...] Read more.
On the basis of the previous models of inductive and steric effects, ‘inductive’ electronegativity and molecular capacitance, a range of new ‘inductive’ QSAR descriptors has been derived. These molecular parameters are easily accessible from electronegativities and covalent radii of the constituent atoms and interatomic distances and can reflect a variety of aspects of intra- and intermolecular interactions. Using 34 ‘inductive’ QSAR descriptors alone we have been able to achieve 93% correct separation of compounds with- and without antibacterial activity (in the set of 657). The elaborated QSAR model based on the Artificial Neural Networks approach has been extensively validated and has confidently assigned antibacterial character to a number of trial antibiotics from the literature. Full article
Open AccessArticle Application of the Extended Grunwald-Winstein Equation to Solvolyses of n-Propyl Chloroformate
Int. J. Mol. Sci. 2005, 6(1), 87-96; doi:10.3390/i6010087
Received: 30 November 2004 / Accepted: 10 December 2004 / Published: 31 January 2005
Cited by 39 | PDF Full-text (94 KB) | HTML Full-text | XML Full-text
Abstract
Application of the extended Grunwald-Winstein equation to solvolyses of n-propyl chloroformate in a variety of pure and binary solvents indicates an addition-elimination pathway in the majority of the solvents but an ionization pathway in the solvents of highest ionizing power and lowest [...] Read more.
Application of the extended Grunwald-Winstein equation to solvolyses of n-propyl chloroformate in a variety of pure and binary solvents indicates an addition-elimination pathway in the majority of the solvents but an ionization pathway in the solvents of highest ionizing power and lowest nucleophilicity. For methanolysis, a solvent deuterium isotope effect of 2.17 is compatible with the incorporation of general-base catalysis into the substitution process. Activation parameters are consistent with the duality of mechanism. Very modest positive salt effects are observed on adding chloride or bromide salts to the ethanolysis. Full article
Open AccessArticle Solvent and Ligand Effects on the Tandem Addition-Lithiation-Electrophilic Substitution of Phenyllithium on α,β-Unsaturated Carbonyl Compounds
Int. J. Mol. Sci. 2005, 6(1), 97-103; doi:10.3390/i6010097
Received: 2 June 2004 / Revised: 15 June 2004 / Accepted: 17 December 2004 / Published: 31 January 2005
PDF Full-text (174 KB) | HTML Full-text | XML Full-text
Abstract
The reaction of phenyllithium with E-cinnamaldehyde is extremely sensitive to the reaction conditions and surprising changes in the product distribution were observed upon changes in the solvent, concentrations, duration or temperature of the reaction. For these reasons the above mentioned reaction was [...] Read more.
The reaction of phenyllithium with E-cinnamaldehyde is extremely sensitive to the reaction conditions and surprising changes in the product distribution were observed upon changes in the solvent, concentrations, duration or temperature of the reaction. For these reasons the above mentioned reaction was considered an appropriate model to examine solvent and aggregation effects of PhLi. On the other hand, when two or trhee equiv of phenyllithium are used, instead of one, the reaction transforms into a surprising tandem addition-lithiation-β-alkylation sequence, that can be successfully applied to the synthesis of substituted dihydrochalcones. The observed effects upon changes in the reaction conditions, as well as the effects of additives that modify the PhLi dimer-monomer equilibrium are consistent with a reaction pathway in which dimeric phenyl lithium attacks to the E-cinnamaldehyde without previous deaggregation. Usually, monomers are found to be more reactive than dimers, but, in this reaction the opposite effect is observed, and the tandem reaction spectacularly decreases with the (PhLi)2 concentration. Full article
Open AccessArticle Influence of Long-Tailed Alcohols on the Solubilisation of Cationic DHAB Bilayers
Int. J. Mol. Sci. 2005, 6(1), 104-118; doi:10.3390/i6010104
Received: 17 February 2004 / Accepted: 19 March 2004 / Published: 31 January 2005
Cited by 3 | PDF Full-text (296 KB) | HTML Full-text | XML Full-text
Abstract
The effects of n-decanol and cetyl alcohol incorporated into cationic di-n-hexadecyldimethylammonium bromide (DHAB) bilayers on the packing and the resistance against solubilisation by Triton X-100 have been investigated. Solubilisation experiments revealed that the mismatch between the C10-tail of n-decanol with [...] Read more.
The effects of n-decanol and cetyl alcohol incorporated into cationic di-n-hexadecyldimethylammonium bromide (DHAB) bilayers on the packing and the resistance against solubilisation by Triton X-100 have been investigated. Solubilisation experiments revealed that the mismatch between the C10-tail of n-decanol with the DHAB-tails does not affect the structural integrity of the vesicles. On the contrary, upon increasing amounts of cetyl alcohol, of which the tail matches in size with the DHAB-tails, breakdown of the vesicles is promoted, whereas complete solubilisation is strongly hampered. The system is further investigated by DSC and cryo-EM experiments. In addition, the effects of n-decanol and cetyl alcohol embedded into DHAB bilayers on the vesicular rate constants for the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate (6-NBIC) suggest that both alcohols affect the structure of the Stern region in an equal manner, leading to a decrease in the catalysis. Therefore, it is concluded that addition of the alcohols leads to changes in properties of the interior of the bilayer, rather than the polar-apolar interface. Full article
Open AccessArticle Thermodynamics of Water-octanol and Water-cyclohexane Partitioning of some Aromatic Compounds
Int. J. Mol. Sci. 2005, 6(1), 119-129; doi:10.3390/i6010119
Received: 4 August 2004 / Revised: 3 February 2005 / Accepted: 3 February 2005 / Published: 31 January 2005
Cited by 15 | PDF Full-text (236 KB) | HTML Full-text | XML Full-text
Abstract
The Gibbs free energy, enthalpy and entropy of partitioning of 45 simple aromatic compounds (phenols, benzoic acids and acetanilides) from water to octanol and from water to cyclohexane have been determined using the filter-probe method. This involved the measurement of partition coefficients [...] Read more.
The Gibbs free energy, enthalpy and entropy of partitioning of 45 simple aromatic compounds (phenols, benzoic acids and acetanilides) from water to octanol and from water to cyclohexane have been determined using the filter-probe method. This involved the measurement of partition coefficients over the temperature range 20-45oC. The aim of the work was to explore the effects of intramolecular hydrogen bonding and steric factors on the partitioning process. It was found that the intramolecular hydrogen bond is intact in 2-nitrophenol and salicylic acid, and possibly in 2-hydroxybenzaldehyde, in all three solvents, but 2-chlorophenol is intramolecularly hydrogen bonded only in inert solution. The evidence indicates that 2-nitroresorcinol and 2,6-dihydroxybenzoic acid possess only one intramolecular hydrogen bond, although they are theoretically capable of possessing two. There is evidence of steric shielding in 2,6-dimethylphenol, whilst 2,6-dimethylbenzoic acid and ortho-substituted acetanilides show evidence of steric twisting of the carboxyl and acetamido groups respectively out of the plane of the aromatic ring. Unusual steric effects are displayed in the methyl-2-nitrophenols whereby, depending upon the position of the methyl group, the intramolecular hydrogen bond is either weakened or strengthened. Full article
Open AccessArticle Reduction of Sulfur Dioxide on Carbons Catalyzed by Salts
Int. J. Mol. Sci. 2005, 6(1), 130-142; doi:10.3390/i6010130
Received: 13 August 2004 / Revised: 21 January 2005 / Accepted: 21 January 2005 / Published: 31 January 2005
Cited by 10 | PDF Full-text (226 KB) | HTML Full-text | XML Full-text
Abstract
The reduction of SO2 on different carbons in the presence of the nitrates and sulfides of sodium, potassium and calcium and potassium polysulfides was studied. The presence of salts increased the initial rate 2-5 fold for all of them and did [...] Read more.
The reduction of SO2 on different carbons in the presence of the nitrates and sulfides of sodium, potassium and calcium and potassium polysulfides was studied. The presence of salts increased the initial rate 2-5 fold for all of them and did not change the product distribution. The catalysis was not determined by the cation and there was no difference in the catalytic reactivity between nitrates and sulfides. The sulfur content of the activated carbon increased during the reaction on account of the stable reactive intermediates in the reduction of SO2. In the presence of NaNO3 or Na2S, the amount of sulfur incorporated was in the molar ratio Na:S = 3 ± 0.3, and the XPS spectra of the residual carbon showed an increase of ca. 9% of the non-oxidized form of sulfur in the intermediates. In the absence of salt, it is proposed that after the adsorption of SO2 on the carbon, a 1,3,2-dioxathiolane or 1,2-oxathietene 2-oxide are formed and that decompose to produce CO2 and atomic sulfur. The non-oxidized sulfur intermediate would be an episulfide 3, formed from the reaction of the atomic sulfur with the nearest double bond and followed by consecutive reactions of insertion of atomic sulfur to form a trisulfide. Extrusion of S2 from the trisulfide would regenerate the episulfide, establishing a sulfidedisulfide-trisulfide equilibrium that worked as a capture-release cycle of sulfur. In the presence of salt, the results are consistent with the assumption that the episulfide 3 reacts with the corresponding sulfide anion to form a disulfide anion, which upon reaction with atomic sulfur forms a trisulfide anion that decomposes releasing diatomic sulfur S2, transporting the sulfur and generating a thiolate that is part of the catalytic cycle. Full article
Open AccessArticle Ab Initio Studies on the Preferred Site of Protonation in Cytisine in the Gas Phase and Water
Int. J. Mol. Sci. 2005, 6(1), 143-156; doi:10.3390/i6010143
Received: 24 June 2004 / Revised: 28 January 2005 / Accepted: 28 January 2005 / Published: 31 January 2005
Cited by 14 | PDF Full-text (237 KB) | HTML Full-text | XML Full-text
Abstract
Ab initio calculations (HF, MP2, DFT for isolated and PCM for solvated molecules) were performed for cytisine (1) and its model compounds: N-methyl-2-pyridone (2) and piperidine (3). Among three heteroatomic functions (carbonyl oxygen, pyridone and piperidine nitrogens) considered as the possible sites [...] Read more.
Ab initio calculations (HF, MP2, DFT for isolated and PCM for solvated molecules) were performed for cytisine (1) and its model compounds: N-methyl-2-pyridone (2) and piperidine (3). Among three heteroatomic functions (carbonyl oxygen, pyridone and piperidine nitrogens) considered as the possible sites of protonation in 1, surprisingly the carbonyl oxygen takes preferentially the proton in the gas phase whereas in water the piperidine nitrogen is firstly protonated. For model compounds, the piperidine nitrogen in 3 is more basic than the carbonyl oxygen in 2 in both, the gas phase and water. Full article
Open AccessArticle Ab initio post-HF CCSD(T) Calculations for Triplet and Singlet Methylene in Four consecutive Dunning Basis Sets with Extrapolations to Infinite Limits for Various Molecular Properties
Int. J. Mol. Sci. 2005, 6(1), 157-176; doi:10.3390/i6010157
Received: 8 October 2004 / Revised: 10 December 2004 / Accepted: 10 December 2004 / Published: 31 January 2005
Cited by 6 | PDF Full-text (333 KB) | HTML Full-text | XML Full-text
Abstract
Stationary points for four geometrically different states of methylene: bent and linear triplet methylene, bent and linear singlet methylene were investigated using the highly reliable post-HF CCSD(T) method. Extrapolations to the CCSD(T) basis set (CBS) limit from Dunning triple to quintuple correlation [...] Read more.
Stationary points for four geometrically different states of methylene: bent and linear triplet methylene, bent and linear singlet methylene were investigated using the highly reliable post-HF CCSD(T) method. Extrapolations to the CCSD(T) basis set (CBS) limit from Dunning triple to quintuple correlation consistent polarized basis sets were performed for total energies, for the equilibrium CH distances re(CH), for singlettriplet separation energies, for energy barriers to linearity and for correlation energies. Post-HF calculations with Dunning basis sets of the literature are presented for comparisons. Full article

Journal Contact

MDPI AG
IJMS Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
ijms@mdpi.com
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to IJMS
Back to Top